Sandblasting process with blastable pressure sensitive adhesive

ABSTRACT

A novel pressure sensitive adhesive (PSA) for use in sandblasting operations to adhere a sandblast mask to a target surface is disclosed. The PSA comprises a non-elastomeric, thermoplastic resin and a tackifier in combination to produce a composition having a Tg of at less than about -40 DEG  C. which is both blastable and water redispersible.

This application is a Divisional of application Ser. No. 08/910,363,filed Aug. 13, 1997, which is a Divisional of application Ser. No.08/718,604, filed Sep. 19, 1996, now abandoned, which is a Continuationof Ser. No. 07/806,924, filed Dec. 11, 1991, now abandoned, whichapplication(s) are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to a pressure sensitive adhesive for use insandblasting operations. In particular, the pressure sensitive adhesiveis based on a water dispersible, thermoplastic, non-elastomeric resinwhich is compounded with a tackifier. This novel material exhibitssurprising properties useful in the surface decoration of articles usingparticulate abrasion.

BACKGROUND OF THE INVENTION

Surface treatment by particulate abrasion is an old and valuableprocess. This is done in primarily two forms: the first involves theapplication of direct physical pressure on the particulate media andrubbing the media across the target surface, e.g., grinding, sanding,polishing, etc.; and the second generally involves the blasting of thetarget surface with air-entrained particulate media, e.g., sandblasting,grit blasting, etc.

Sandblasting technology has been used for a number of years to decoratethe surface of articles in a predetermined pattern. To achieve thisdecoration, particulate abrasive media such as steel grit, slag, sandand other forms of silicone oxide, and aluminum oxide are propelled athigh velocities against the target surface. In order to control theareas of the target surface which are actually abraded by the blastingmedia, a patterned mask is applied to the surface. In the past, suchmasks were prepared manually from rubber, paper, or other material whichcould withstand penetration by the abrasive media, and they were appliedto the target surface using an adhesive, carefully applied to the maskitself. Any adhesive which extended into the void areas of the mask weredetrimental, as it often acted as an extension of the mask. Thisadhesive extension of the mask results in inaccuracies in the etchedpattern produced by the sandblasting.

A more recent innovation in sandblasting operations is the use ofphotoimageable masks or photoresists. These photoresists comprise aphotosensitive polymeric material which, upon selective exposure tolight of a particular wavelength range, forms regions of two distincttypes: those which are removable by a developer liquid and those whichare unaffected by the developer. These removable and unremovable regionsthen form void areas and mask areas after developing. When thephotoresists is applied to a target surface, the void areas allow theparticulate abrasive media to strike the target surface, while the maskareas protect the underlying target surface from the particulate media.

There have been a number of different approaches to the problem ofattaching the photoresist to the target surface. One approach isexemplified by Nakamura et al., U.S. Pat. Nos. 4,456,680 and 4,587,186wherein the photoresist itself exhibits pressure sensitive adhesiveproperties. However, this approach requires the use of a liquidphotosensitive material and careful preparation of the pressuresensitive adhesive photoresist. This involved preparation of thephotoresist requires the user to be rather sophisticated and essentiallyprecludes the use of the technology by small job shops.

Another approach requires the use of a liquid pressure sensitiveadhesive forming composition which can be applied to the photoresistmask as a discrete layer. Again, if these pressure sensitive adhesiveproducts are not carefully applied to the photoresist, they can act as aphotoresist themselves as discussed above. Therefore, great accuracy isneeded in the application of these adhesives to the photoresist to avoidovershoot of the adhesive into the void areas of the photoresist. Inorder to achieve this accuracy, especially in applications requiringvery fine photoresists, time consuming manual application of theadhesive or an expensive adhesive application machine is required.

In addition, there are several products available on the market forgeneral use in graphic arts. These adhesives are useful for applicationof photoresist masks or general mounting of graphic arts materials andinclude elastomer based products such as 3M PHOTO MOUNT adhesive,available from 3M Co., and CAMIE 350, available from Camie Campbell,Inc. However, these adhesive compositions also are less than desirable.While, with the proper application weight, these adhesives may bepenetrated and removed by the blasting media where exposed by the mask,the adhesives are not water redispersible. Therefore, to remove thesandblasting masks after the blasting operation, hazardous solvents areneeded.

In view of the current state of the sandblasting adhesive art, there area number of failings visible. Therefore, a new pressure sensitiveadhesive useful to adhere sandblast masks having very high resolution totarget surfaces is needed which is easy to use, versatile, blastable,and water redispersible. Such an adhesive would avoid the need for usinggreat care and accuracy in the application of the adhesive and usinghazardous organic solvents to remove the mask after blasting.

SUMMARY OF THE INVENTION

With an eye to overcoming the problems inherent in previous pressuresensitive adhesives used in sandblasting operations, a surprising, new,water redispersible and blastable pressure sensitive adhesive (PSA)composition has been developed. The PSA includes a non-elastomeric,thermoplastic resin and a tackifier. This combination of thermoplasticresin and tackifier forms a composition having a T_(g) of less thanabout -40° C. The term "blastable", as used in the specification and theclaims, means materials which are essentially immediately removed insandblasting operations by the impact of particulate abrasive media. Inother words, the material does not significantly prevent the particulatemedia from abrading the target surface. The term "non-elastomeric", asused in the specification and the claims, means materials which do notmeet the American Society for Testing and Materials definition ofelastomer, "a polymeric material which at room temperature can bestretched to at least twice its original length and upon immediaterelease of the stress will return quickly to approximately its originallength."

The PSA may be formed by the driving of an aqueous mixture having amajor portion of water, about 5 to 30 wt-% of a non-elastomeric,thermoplastic resin, and about 1 to 15 wt-% of a tackifier resin. Theaqueous mixture may be applied to the target surface prior to theapplication of the photoresist mask to form a PSA layer on the targetsurface. The mask is then applied to the PSA layer, and the object isthen sandblasted. In addition, the PSA may be applied to a photoresistmask for application to the target surface to form a photoresist masklaminate. Thus, the new PSA can be used to adhere a separate photoresistask to a target surface, or it can be incorporated in a reformedphotoresist mask laminate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Aqueous Adhesive Composition

The aqueous adhesive composition comprises a major proportion of water,about 5 to 30 wt-% of a non-elastomeric, thermoplastic resin, and about1 to 15 wt-% of a tackifier resin. The aqueous adhesive compositionoptionally includes an organic solvent, a surfactant, a defoaming agent,and a plasticizer. The aqueous composition can be applied to a surfaceand dried to form a pressure sensitive adhesive which is both waterredispersible and blastable.

The non-elastomeric, thermoplastic resin is the base, film-forming resinof the PSA composition. The thermoplastic resin contributes greatly tothe ultimate properties of the PSA composition, and the resin should,therefore, be selected with this in mind. As the PSA is waterredispersible, it is important that the thermoplastic base resin itselfbe water redispersible. The phrase "water redispersible", as used in thespecification and the claims, means that the material described iscapable of being dispersed and reclaimed by an aqueous solution afterbeing dried to form a pressure sensitive adhesive. This term thereforeincludes materials which are soluble, emulsifiable, suspendable, as wellas dispersible in water and other aqueous solutions.

Thus, a representative, non-limiting list of potential thermoplasticbase resins includes polyvinyl alcohol, polyvinyl acetate, vinyl acetatecopolymers such as ethylene-vinyl acetate, polyvinyl pyrrolidone, vinylpyrrolidone copolymers such as vinyl pyrrolidone-vinyl acetate and vinylpyrrolidone-acrylic acid, and polyurethane. These resins have potentialfor use in the present invention both individually and in combinationwith one another. Resins which have a molecular weight in the range ofabout 10,000 to 400,000 are useful in the novel PSA compositions of theinvention. However, when selecting a particular resin and molecularweight thereof, the effect of this selection on the blastability of thePSA should be considered. While not expecting to be held to this theory,it is believed that increased toughness of the base resin tends todecrease the blastability of the resulting compounded PSA.

In addition, the solid phase of the adhesive composition includes atackifier to increase the tack, adhesion, and cohesion of the PSA. Thereare a number of generic classes of tackifier including natural rosin,modified rosin, rosin ester, and synthetic hydrocarbon resin tackifiers.Like the base resin, the tackifier is preferably water redispersible, atleast in its compounded form in the PSA. The tackifier should becompatible with the base resin in order that the tackifier and baseresin form a substantially uniform mixture when applied as a PSA. Whilenot expecting to be held to this theory, it is believed that thetackifier acts to increase the tack of the compounded PSA to glass andto "dilute" the base resin to increase the blastability of the PSAapplied to the target surface without significantly reducing tack.Therefore, the tackifier should also be selected for its contributionsto the properties of the compounded PSA. Factors to be considered inselecting a tackifier include its chemical structure (e.g., aromaticssuch as alpha-methyl styrene, aliphatics such as C₅ aliphatic resins,and polar tackifiers such as rosin esters), molecular weight (typicallybetween about 200 and 2,000), molecular weight distribution, andcompatibility. Because of their generally excellent compatibility with abroad range of film-forming resins, rosin esters are preferred.

Optional components in the aqueous adhesive composition include asurfactant, a defoaming agent, a plasticizer, a stabilizer, and anorganic solvent. An effective amount of an ionic or nonionic surfactantsuch as a carboxylic acid salt, a sulfonic acid salt, a quaternaryammonium salt, a polyoxyethylenated alkyl phenol, or an ethyleneoxide-propylene oxide copolymer may be employed to increase thedispersibility of the solid phase within the aqueous phase of theadhesive composition. An effective amount of a defoaming agent such as2-octanol, a sulfonated oil, an organic phosphate, a silicon fluid, orpolydimethylsiloxane may also be helpful to reduce the amount of foamgenerated during the use of the aqueous adhesive composition. Aplasticizing amount of a plasticizer such as a phthalate, a dibenzoate,a phosphate, an adipate, a sorbitol, a glycol, or a glycerin may also behelpful to improve the pressure sensitive adhesive properties of thecompounded PSA. However, the use of these plasticizers is balancedagainst their potential to reduce the blastability and waterredispersibility of the PSA. An effective amount of a stabilizer such asa freeze-thaw stabilizer or freezing point depressant, an antioxidant ora UV-stabilizer may also be helpful to stabilize the aqueous compositionduring numerous freeze-thaw cycles, etc. A minor amount of an organicsolvent such as a lower alcohol, a lower hydrocarbon, a lower ketone, ora mixture thereof may also be included to improve the dispersion of thesolid phase in the aqueous phase of the adhesive composition. Finally,other optional components such as dyes, pigments, and fillers may beincluded in the aqueous adhesive composition as desired as long as theydo not substantially interfere with the function of the PSA insandblasting operations.

PSA Film

The aqueous adhesive composition can be applied to a substrate and driedto form PSA film. This dried PSA film is both water redispersible andblastable. The PSA is effective in adequately adhering an imaged anddeveloped photoresist mask to a target surface during processing. Thisis surprising as high tack, water soluble PSA are generally expected tobe very tough and resilient. These properties would not appear tocontribute to blastability, etc. However, this PSA film is effective insecuring a photoresist mask to a target surface. There are a number ofproperties which contribute to the usefulness of the PSA film in thisapplication. The PSA film has a T_(g) of less than about -40° C. This isa measure of the softness, flexibility, film state (continuous ordiscontinuous), etc. of the polymeric material. If the T_(g) of the PSAis too high, the PSA will generally be too brittle to be effective,exhibit poor tack, and result in a generally discontinuous film at roomtemperature; if the T_(g) is too low, the PSA will generally be tooelastomeric to be effectively blastable. In addition to the T_(g), therelative adhesion of the PSA to the photoresist and target surface andbetween various layers of a photoresist laminate, and "SandblastResistance", a custom test which is described below. These tests help toqualify PSA's for use in adhering photoresist masks to target surfacesfor abrasive decorating processes.

Generally, the PSA should provide sufficient adhesive strength betweenthe photoresist mask layer and the target surface to prevent theabrasive decorating process from blasting away portions of thephotoresist mask. In addition, when the photoresist mask is a laminatecomprising a plurality of layers, some of which are removed afteradhering of the laminate to the target surface, the adhesion between thephotoresist mask layer and the target surface provided by the PSA shouldbe greater than the adhesion between any release liner and layer of thephotoresist laminate which is in contact with the photoresist masklayer. This may be called the "transferability" of the photoresist mask.Thus, the photoresist mask is transferable if a photoresist laminate canbe applied to a target surface, the laminate prepared for an abrasiveblasting process, and the photoresist mask remains intact as applied onthe target surface.

Finally, the Sandblast Resistance test is an effective test whichpredicts the blastability of the PSA film. As defined above, a blastablematerial is a material which is essentially immediately removed in asandblasting operation by the impact of particulate abrasive media. TheSandblast Resistance test proceeds in the following manner:

Blast Resistance Test

Materials Required:

(1) Blasting media (Aluminum Oxide, 160 U.S. Std. Mesh)

(2) Pressurized sandblasting system

(a) Cabinet

(b) Airline pressure of 20 psi

(c) Nozzle (0.25" diameter)

(3) Test Panel Preparation

(a) Glass plate (approx. 4"×8")

(b) #12 Mayer Rod

(c) Coating material (16 wt-% solids)

Procedure:

1. Coat glass test panel with coating material using #12 Mayer rod toobtain about 5.2 g/m² coating on glass panel (dry coating deposit).

2. Air dry test panels.

3. Place coated test panel in sandblast cabinet.

4. Aim sandblast nozzle perpendicular to test panel, maintaining adistance between nozzle and panel of five inches.

5. Activate sandblasting apparatus to blast test panel for five seconds.

6. Repeat steps 4-5 in several different locations on the test panel.

7. Remove test panel from cabinet, removing abrasive media remaining onpanel.

8. Remove test coating from test panel using appropriate solvent.

9. Dry test panel in oven and inspect etching in glass panel.

10. Record findings--Yes (etching), No (panel unetched).

Method of use of the Aqueous Adhesive Composition

The aqueous adhesive composition can be prepared by mixing thecomponents in any suitable mixing vessel. It may be helpful toincorporate the solid components as aqueous emulsions into the adhesivecomposition. Thus, the base resin may be introduced into the adhesivecomposition as an emulsion of the resin itself or in a compounded formwith a plasticizer and/or a tackifier. Preferably, the base resin isintroduced as an aqueous emulsion of the resin with a minor amount ofplasticizer and tackifier, and additional tackifier may be introduced asan aqueous emulsion. The optional components may be added in any orderpractical, however, it may be helpful to introduce the defoaming agentinto the mixing vessel at an early stage to minimize foam generatedduring preparation. The aqueous adhesive may be used immediately, or itmay be transported and/or stored until use.

The aqueous adhesive composition may be applied to any substrate anddried to form the PSA. The drying of the aqueous composition topreferably monitored to avoid complete drying and the resulting loss ofdry tack and other PSA qualities. The aqueous composition is preferablydried sufficiently to substantially eliminate liquid flow of thecomposition and to provide dry tack. If the PSA is not to be usedimmediately, a release liner is preferably applied to the exposedsurface of the PSA film to avoid overdrying the film. Those of ordinaryskill in the art will recognize the appropriate level of drying toprovide PSA qualities without overdrying the film.

In one mode of a sandblasting operation, the aqueous adhesivecomposition can be applied directly to a target surface and dried inplace in order to provide a PSA film for the application of thephotoresist mask. The PSA may be applied on any target surface whichwill not be damaged by the aqueous phase of the adhesive compositionprior to drying. In particular, it is contemplated that the PSA will beused on target surfaces of glass, metal, wood, ceramic, stone, etc.

The photoresist mask may then be applied directly to the PSA film suchthat the mask layer itself is adhered to the PSA film on the targetsurface. Any release liners on the photoresist mask can then be removedto expose the mask for the blasting of the mask and target surface byparticulate abrasive media. The photoresist mask may be a mask laminateincorporating a top, destroyable carrier film layer for dimensionalstability and protection of the mask layer during use. Again,particulate abrasive media such as steel grit, slag, sand and otherforms of silicon oxide, and aluminum oxide can then be propelled at highvelocities against the PSA-coated target surface and photoresist mask.The media penetrates and removes the destroyable carrier film, ifpresent, and the PSA film exposed by the void areas of the mask. Theblasting continues until a desired abrasion of the target surface isachieved. The target surface and adhered mask may then be treated withan aqueous solution to redisperse the PSA film layer thereby allowingthe removal of the photoresist mask. In this manner, very fine abradedpatterns may be formed in the target surface.

In a second mode of operation, a photoresist mask laminate comprising aPSA layer may be prepared. Such a mask laminate may be formed of aphotoresist mask and the dried PSA material. Preferably, the masklaminate comprises (a) a photoresist mask layer which comprises voidareas and mask areas to selectively expose through the void areas anunderlying pressure sensitive adhesive composition, (b) the dried PSAmaterial disposed upon the lower surface of the photoresist mask layer,and (c) a destroyable carrier film layer disposed on the upper surfaceof the photoresist mask layer. Thus, the carrier film layer and thepressure sensitive adhesive composition cooperate to essentiallyenvelope the photoresist mask. More preferably, this mask laminateincludes a first release liner on the outside of the destroyable carrierfilm layer and a second release liner on the outside of the PSA layer.Of course, the mask laminate could have a top and bottom release linerwithout the destroyable carrier film layer.

In operation, the second release liner is removed from the PSA layer,and the mask laminate is securely adhered to the target surface. Next,the first release liner is removed from the top of the destroyablecarrier film layer. The masked target surface is then ready to beblasted as described above. The media penetrates and removes thedestroyable carrier film, if present, and the PSA film exposed by thevoid areas of the mask. The blasting continues until a desired abrasionof the target surface is achieved, and the target and mask are cleanedwith an aqueous solution, as described above.

Photoresist masks used in the practice of this invention are generallypolymeric photoresists. Preferably, the photoresist mask comprises aphotoresist layer as disclosed in Van Iseghem, U.S. Pat. No. 4,764,449,which is hereby incorporated by reference. This photoresist mask layercomprises a negative photosensitive composition which interacts withlight of a particular wavelength to transform from a soluble state to aninsoluble state. A preferred photoresist composition comprises across-linkable polymer composition including a polymer having pendanthydroxyl groups to react with a sufficient concentration of aphotoinitiator cross-linking specie. Preferably, the photocross-linkablepolymer composition comprises homo- and copolymers of polyvinyl alcohol.Preferred photoinitiator cross-linking species include diazonium saltphotocross-linkers. The preferred photoresist composition may alsoinclude a water insoluble film-forming polymeric binding agent such ascellulosic compounds, and water insoluble homo- and copolymers made ofstyrene, methylmethacrylate, vinyl acetate, vinyl butyral, ethylene,propylene, alkylene oxide monomers, and maleic anhydride. Additionalcomponents such as plasticizers, surfactants, sensitizers, etc., mayalso be incorporated into the photoresist mask layer.

The optional destroyable carrier film is preferably easily destroyableby sandblast media so it does not interfere with the ultimateperformance of the mask. In addition, the carrier film is preferablynon-elastomeric to provide dimensional stability to the laminate. Anypolymeric or metallic film may be used as the carrier film if itexhibits the above characteristics. It is preferred that the carrierfilm be about 1 to 5 microns in thickness. This thickness providessufficient dimensional stability while not providing too great animpediment to sandblast media. A representative, non-limiting list ofuseful carrier film materials includes metallic films such as copper andaluminum; polymeric films such as polyvinyl butyral, polyvinyl formal,polyethylene-vinylacetate copolymers, polyolefins, nitrocellulose,polyvinyl chloride; and other materials such as paper.

The photoresist laminate may also include at least one release liner toprotect the mask. The release liner should contact the support membraneand photosensitive layer with a surface having low surface energy. Thisis typically achieved by coating a film with a thin layer of a releaseagent or release liner such as silicone, electron beam (EB) curedrelease coating, polytetrafluoroethylene (PTFE), or UV curable releasecoating. Preferably, the release liner comprises a polyolefin film suchas polypropylene, or polyethylene, a polyester film such as polyethyleneterephthalate, or MYLAR.

EXAMPLES

The following examples are provided to promote an understanding of theinvention and contain a best mode.

    ______________________________________                                        EXAMPLE 1                                                                     ______________________________________                                        1.      Polyvinylpyrrolidone-based                                                                          40.1                                                  adhesive*                                                                 2.  Water                                  40.1                               3.  Defoaming agent (BUBBLE BREAKER       0.3                                     3056A Witco Chemical)                                                     4.  Silicone glycol copolymer, HLB       0.5                                      value 8.0-11.0; (SILWET L7607,                                                Union Carbide)                                                            5.  Ester Gum tackifier emulsion       9.0                                        (NOPCO EB, Henkel Corp.)                                                  6.  Isopropanol                            10.0                                 100.0                                                                     ______________________________________                                    

Ingredients 1 through 4 were weighed out and mixed together for 5minutes. Ingredients 5 and 6 were added under agitation to the initialmix. The mixture was allowed to stand at room temperature forapproximately 1 hour. The mixture was coated on a sheet of glass (4"×8")by a #12 Mayer rod. The coating was dried in a convection oven for 10minutes at 120° F.

A piece of pre-imaged sandblast resist mask having a release liner,destroyable carrier film and an imaged and developed photoresist masklayer was applied under hand pressure to the piece of glass. The releaseliner was removed from the carrier film and photoresist mask withoutdamaging the photoresist mask.

The glass was sandblasted by aluminum oxide (160 U.S. Std. Mesh) by apressure pot sandblasting unit at 30 psi for about 1 minute. The glasspanel was washed with hot water to remove sand, the mask, and theadhesive coating, and dried. The resulting glass panel showed a uniformpattern of etching and no sign of interference with the etching due tothe adhesive. The adhesive was blasted very easily and washed away veryeasily with water.

    ______________________________________                                        EXAMPLE 2                                                                     ______________________________________                                        1.       The polyvinyl pyrrolidone adhesive                                                                 30.0                                                  of Example 1                                                              2.  Water                                 37.5                                3.  Defoaming agent (FOAM MASTER VT       2.0                                     defoamer, Henkel Corp.)                                                   4.  An ethoxylated alkyl phenol      1.0                                          surfactant (IGEPAL CO-210, GAF)                                           5.  Ester Gum tackifier emulsion      15.0                                        (NOPCO EB, Henkel Corp.)                                                  6.  Methanol                              14.5                                                                          100.0                             ______________________________________                                    

The components are mixed and applied as in Example 1. The glass panel iswashed with hot water to remove sand, the mask, and the adhesivecoating, and dried. The resulting glass panel shows a uniform pattern ofetching and no sign of interference with the etching due to theadhesive. The adhesive is blasted very easily and washed away veryeasily with water.

    ______________________________________                                        EXAMPLE 3                                                                     ______________________________________                                        1.      Polyvinyl Acetate homopolymer                                                                       50.0                                                  emulsion, 55% solids in water                                             2.  Plasticizer (BENZOFLEX 50,       27.0                                         Velsicol Chemical)                                                        3.  Defoaming agent (FOAM MASTER VT,       2.0                                    Henkel Corp.)                                                             4.  Silicone glycol copolymer, HLB       1.0                                      value 8.0-11.0; (SILWET L7607,                                                Union Carbide)                                                            5.  Ester Gum tackifier emulsion       20.0                                       (NOPCO EB, Henkel Corp.)                                                                                             100.0                            ______________________________________                                    

The components are mixed and applied as in Example 1. The glass panel iswashed with hot water to remove sand, the mask, and the adhesivecoating, and dried. The resulting glass panel shows a uniform pattern ofetching and no sign of interference with the etching due to theadhesive. The adhesive is blasted very easily and washed away veryeasily with water.

    ______________________________________                                        EXAMPLE 4                                                                     ______________________________________                                        1.      Polyvinyl Alcohol, degree of                                                                        50.0                                                  Hydrolysis = 71-89, Low MW grade,                                            25% solution                                                               2. Glycerol                                   20.0                            3. Polyvinyl Acetate homopolymer   10.0                                          emulsion, 55 wt-% solids                                                   4. Dibutyl Phthalate Plasticizer              2.5                             5. Ester Gum tackifier emulsion   10.0                                          (NOPCO EB, Henkel Corp.)                                                    6. Defoaming agent (BUBBLE BREAKER          2.0                                  3056A Witco Chemical)                                                      7. Silicone glycol copolymer, HLB          1.0                                   value 8.0-11.0; (SILWET L7607,                                                Union Carbide)                                                             8. Isopropanol                                4.5                                                                           100.0                         ______________________________________                                    

The components are mixed and applied as in Example 1. The glass panel iswashed with hot water to remove sand, the mask, and the adhesivecoating, and dried. The resulting glass panel shows a uniform pattern ofetching and no sign of interference with the etching due to theadhesive. The adhesive is blasted very easily and washed away veryeasily with water.

    ______________________________________                                        EXAMPLE 5                                                                     ______________________________________                                        1.      Vinylpyrrolidone/vinyl acetate                                                                      30.0                                                  copolymer, agueous dispersion,                                                25% solids; MW = 40,000 to 160,000;                                           Vinylpyrrolidone/vinyl acetate ratio                                          =  70/30 to 30/70                                                         2.  Partially hydrolyzed PVA, degree of      40.0                                 Hydrolysis = 71-89, Low MW grade,                                             25% solution                                                              3.  Defoaming agent (FOAM MASTER VT,       2.0                                    Henkel Corp.)                                                             4.  An ethoxylated alkyl phenol       5.0                                         surfactant (IGEPAL CO-210, GAF)                                           5.  Ester Gun tackifier emulsion       10.0                                       (NOPCO EB, Henkel Corp.)                                                  6.  Glycerol                                      4.0                         7.  Isopropanol                                   9.0                                                                           100.0                     ______________________________________                                    

The components are mixed and applied as in Example 1. The glass panel iswashed with hot water to remove sand, the mask, and the adhesivecoating, and dried. The resulting glass panel shows a uniform pattern ofetching and no sign of interference with the etching due to theadhesive. The adhesive is blasted very easily and washed away veryeasily with water.

Example 6

The adhesive of Example 1 was coated over an imaged and developedphotoresist mask layer using a #12 Mayer rod of a laminate having themask layer, a destroyable carrier layer of polyvinyl butyral, and arelease liner. The resulting photoresist mask laminate was dried forabout 3 minutes at 120° F. The photoresist mask laminate was adheredwith hand pressure, rolling the laminate onto a spherical glass jar. Therelease liner was removed from the laminate, and the remaining laminateremained well-adhered to the jar. The glass jar was sandblasted as inExample 1. The jar was then washed with hot water to remove the blastingmedia, photoresist mask, and the adhesive and subsequently dried in anoven. The etched pattern in the jar was very uniform, and it did notshow any evidence of interference with the pattern from the adhesivelayer. The adhesive exposed through the mask was blasted away veryeasily.

Example 7

Several PSA's of various classifications were subjected to the SandblastResistance Test described above. In addition, the adhesives were testedfor water redispersibility by rinsing with hot water (about 50° C.) forabout two minutes. The results are illustrated below in Table I.

                  TABLE I                                                         ______________________________________                                        PSA Type         Blastability                                                                              Redispersibility                                 ______________________________________                                        Acrylate                                                                        (Ashland Chemical 2302-W-60)   Yes            No                              Acrylate                                                                      (Rohm & Haas ROBOND PS-61)     Yes            No                              Elastomeric (CAMIE 350)*       No             No                              The polyvinylpyrrolidone                                                      adhesive of Example 1                                                         (ingredient 1.)                Yes            Yes                             Example 1                      Yes            Yes                           ______________________________________                                    

From the above data, it can be seen that the elastomeric PSA is notblastable. In addition, the elastomeric PSA and the acrylate PSA's werenot water redispersible. The only Blastable and redispersible PSA's werethe polyvinylpyrrolidone based materials. However, only the PSA ofExample 1 exhibits transferability wherein the photoresist mask is notblasted off of the target surface during a sandblasting operation.

Although the present invention has been described with reference to theabove particular discussion and examples, it should be understood thatthose skilled in the art may make many other modifications withoutdeparting from the spirit and scope of the invention as defined by theappended claims.

What is claimed is:
 1. A process for decorating a target surface byforming a patterned abraded design in the surface, which processcomprises the steps of:(a) applying to the target surface a pressuresensitive adhesive composition which comprises:(i) a major portion ofwater; (ii) about 5 to 30 wt-% of a non-elastomeric, thermoplasticresin; and (iii) about 1 to 15 wt-% of a rosin ester tackifier;whereinthe adhesive composition dries to form a water redispersible andblastable pressure sensitive adhesive film having a T_(g) of less thanabout -40° C.; (b) adhering an imaged and developed photoresist mask tothe pressure sensitive adhesive film on the surface opposite the targetsurface wherein the photoresist mask comprises void areas and mask areasto selectively expose through the void areas the underlying pressuresensitive adhesive film; (c) delivering particulate abrasive media highvelocities to and through the exposed portions of the pressure sensitiveadhesive film to selectively expose the target surface; (d) deliveringparticulate abrasive media at high velocities to the exposed portions ofthe target surface to form a patterned, abraded design therein; and (e)redispersing the pressure sensitive adhesive film in an aqueoussolution, thereby removing the photoresist mask from the targetsurface;wherein the adhesive film provides adhesion between the imagedand developed photoresist mask layer and the target surface sufficientto prevent undesired removal of the photoresist mask layer prior toredispersing the pressure sensitive adhesive film in the aqueoussolution.
 2. The process of claim 1 wherein the non-elastomericthermoplastic resin is a polyvinyl alcohol, a polyvinyl acetate, apolyurethane, or a mixture thereof.
 3. The process of claim 1 whereinthe non-elastomeric thermoplastic resin is a vinylpyrrolidone homo- orcopolymer.
 4. The process of claim 1 wherein the non-elastomericthermoplastic resin is a copolymer of a polyvinyl acetate, or apolyvinyl alcohol.
 5. The process of claim 1 wherein the tackifier resinis a natural rosin, a modified rosin, a hydrocarbon resin, or a mixturethereof.
 6. The process of claim 1 wherein the tackifier resin is arosin ester.
 7. The process of claim 1 wherein the particulate abrasivemedia comprises aluminum oxide or silicone oxide.
 8. A process fordecorating a target surface by forming a patterned abraded design in thesurface, which process comprises the steps of:(a) applying to the targetsurface a sandblast mask laminate which comprises:(i) an imaged anddeveloped photoresist mask layer having an upper surface and a lowersurface wherein the photoresist mask layer comprises void areas and maskareas to selectively expose through the void areas an underlyingpressure sensitive adhesive composition; (ii) a pressure sensitiveadhesive composition having a T_(g) of less than about -40° C. disposedupon the lower surface of the photoresist mask layer which comprises:(A)about 50 to 99 wt-% of a non-elastomeric, thermoplastic resin; and (B)about 1 to 50 wt-% of a tackifier; (iii) a destroyable carrier filmlayer disposed on the upper surface of the photoresist mask layerwherein the carrier film layer and the pressure sensitive adhesivecomposition cooperate to essentially envelope the photoresist masklayer; and (iv) a release liner in contact with the surface of thedestroyable carrier film layer opposite the photoresist masklayer;wherein the pressure sensitive adhesive composition is waterredispersible and blastable and the laminate is applied to the targetsurface by adhering the pressure sensitive adhesive composition to thetarget surface; (b) delivering particulate abrasive media at highvelocities to and through destroyable carrier film layer to exposephotoresist mask layer and the pressure sensitive adhesive film; (c)delivering particulate abrasive media at high velocities to and throughthe exposed portions of the pressure sensitive adhesive film toselectively expose the target surface; (d) delivering particulateabrasive media at high velocities to the exposed portions of the targetsurface to form a patterned, abraded design therein; and (e)redispersing the pressure sensitive adhesive film in an aqueoussolution, thereby removing the photoresist mask from the targetsurface;wherein the adhesive film provides adhesion between the imagedand developed photoresist mask layer and the target surface sufficientto prevent undesired removal of the photoresist mask layer prior toredispersing the pressure sensitive adhesive film in the aqueoussolution.
 9. The process of claim 8 wherein the non-elastomericthermoplastic resin is a polyvinyl alcohol, a polyvinyl acetate, apolyurethane, or a mixture thereof.
 10. The process of claim 8 whereinthe non-elastomeric thermoplastic resin is a vinylpyrrolidone homo- orcopolymer.
 11. The process of claim 8 wherein the non-elastomericthermoplastic resin is a copolymer of a polyvinyl acetate, or apolyvinyl alcohol.
 12. The process of claim 8 wherein the tackifierresin is a natural rosin, a modified rosin, a hydrocarbon resin, or amixture thereof.
 13. The process of claim 8 wherein the tackifier resinis a rosin ester.
 14. The process of claim 8 wherein the particulateabrasive media comprises aluminum oxide or silicone oxide.
 15. A processfor decorating a target surface by forming a patterned abraded design inthe surface, which process comprises the steps of:(a) imaging anddeveloping a photosensitive laminate comprising:(i) a photoresist masklayer having an upper surface and a lower surface comprising a watersoluble vinyl polymer having pendant hydroxyl groups capable ofphotogenerated insolubility which layer is developable with aqueousmedia to form mask areas and void areas; (ii) a destroyable carrier filmlayer disposed on the upper surface of the photoresist mask layer; and(iii) a release liner in contact with the surface of the destroyablecarrier film layer opposite the photoresist mask layer; (b) applying tothe target surface an aqueous adhesive composition which comprises:(i) amajor portion of water; (ii) about 5 to 30 wt-% of a non-elastomeric,thermoplastic resin; and (iii) about 1 to 15 wt-% of a rosin estertackifier;wherein the adhesive composition dries to form a waterredispersible and blastable pressure sensitive adhesive film having aT_(g) of less than about -40° C.; (c) adhering to the pressure sensitiveadhesive film on the surface opposite the target surface the imaged anddeveloped photoresist mask layer of the photoresist laminate wherein thevoid areas of the photoresist mask layer selectively expose theunderlying pressure sensitive adhesive layer; (d) separating the releaseliner from the destroyable carrier film layer; (e) deliveringparticulate abrasive media at high velocities to and through destroyablecarrier film layer to expose photoresist mask layer and the pressuresensitive adhesive film; (f) delivering particulate abrasive media highvelocities to and through the exposed portions of the pressure sensitiveadhesive film to selectively expose the target surface; (g) deliveringparticulate abrasive media at high velocities to the exposed portions ofthe target surface to form a patterned, abraded design therein; and (h)redispersing the pressure sensitive adhesive film in an aqueoussolution, thereby removing the photoresist mask from the targetsurface;wherein the adhesive film provides adhesion between the imagedand developed photoresist mask layer and the target surface sufficientto prevent undesired removal of the photoresist mask later prior toredispersing the pressure sensitive adhesive film in the aqueoussolution.